Does anyone have a good analogy of the relationship between nitro and speed?

What happens on opposite ends of the nitro curve? Too much nitro? Not enough?

What about compression? How does this fit into the mix? How do you know when you need more nitro or less, and which temperature glow plug to use? (ie., what signs should we be looking for to find the proper mix to have a nice strong, high rpm turning motor.)

Motors seem to run fine on 10-15% but not on 50-60%! Why?

What's the plug temp got to do with any of this? Relation?


All serious questions here. I'm trying to get a very clear idea of how this complicated mix of ingredients all work together efficiently.

[sm=cool.gif]


Thank You!

Randy Ritch of Rictches Brew is the man to talk to down here in Texas, Only thing is it,s vary hard to get a hold of him because he has so many things going on at one time.

Nitro makes power. But the question is why. Partly due to it's ability to burn in heavy fuel/air mixtures. The thing that moves the piston is pressure and mass. If you pick up a can of 65% fuel and compare it with 15% fuel you will notice the 65% is much heavier. When I was flying Formula One, I would break in the engines on 15% before running the 65%. The difference in needle vavle setting was that the needle was turned one full turn out for the 65% compared to the 15%. So a much higher volume of heavier fuel doing the work. It worked out to be around 3 oz. of fuel per minute in a .40.

You generally need to raise the head for the higher nitro. Plugs we used were the K&B 1L plugs, then later the Nelson types. Plugs only last for one flight, so expect $6 to 8 per flight for plugs and fuel. And the piston tends to go away with the slightest of lean run. Deck height become more of an issue with changes in air pressure, temperature and humidity. You have to learn to "read" the plug. It should be shiny wet looking after a good run with slight distortion of the element. If the element pushes in or pulls out the compression is wrong. If it is gone and/or the plug body is dry, you were too lean. If you were way too lean, the black stuff on the side of your fuselage will be a mixture of oil and metel from your piston.

It is better to start off with the head too high and a light load for the prop. With this set-up, the needle will be very broad and easy to set. As you come down on the head, you will find the needle starts to get peaky and hard to set.

That's a good description of R/C racing in general.

What about Fai plane they use no nitro yet turn out a great deal of energy?

Nanu,

That's the pipe. Interestingly, back in the 1980s and 1990s the Formula 1 and FAI (F3D) racers had very similar size, weight, wing thickness, etc., and the same engine displacement (.40 cu. in./6.5 cc), and they achieved almost identical speeds using two radically different approaches to extracting power from the engine. One used unlimited nitro but exhaust tuning was prohibited; the other used unlimited exhaust tuning but nitro was prohibited.

I'm told that straight alcohol and oil (FAI fuel) actually packs more Btu than nitro, but you need the tuned exhaust and a high temperature to get it out. I don't know about that. I do know that you can go pretty darn fast if you take an F3D airplane and spike the fuel with just a little bit of nitro. When I was test-flying my F3D airplane at 5,000 feet elevation, I used 7.5% nitro so that the rpm and flight characteristics would be about the same as at sea level using FAI fuel. But I never had the need (or the courage) to push the engine any harder than that.

Duane Gall
RCPRO

WOW,
I was under the impression that Nitro made more power because of the Oxygen in the chain.
Sorta like a cheap way of supercharging.

Silly me.[8D]